Method of preparing a photosensitive blood albumin lithographic solution



Patented Jan. 20, 1948 UNITED STATES PATENT IQEFJFICE .-METI-I@D OF"PREPARING A PHOTOSENSI- .TIVE 'BLOOD "SOLUTION ALBUMIN .,.LI-THOGRAPHIC aCharlesHTVan Dusen, Jr., Willoughby," 0hi0, as- I signor'to Addressograph-Multigraph Corporation, Gleveland, Ohio,- a corporationsofJDelaware N0 Drawing. Application August"7,.1944, Serial No. 548,515

2 Claims.

This invention relates toajphoto-sensitive lithographic solution and to -:a method of prepar- -inggthe-rsame.

'Ithas been-common practice heretofore to .uti-

:lize an .;=aqueous egg albumin-ammonium .di-

.which decomposes the ammonium dichromate and causes it :to exert aso-called tanning or hardening-effect upon-the albumin. The plate is ithen coated with a soecalled fatty or greasy lithographic printing ink and the unexposed or untanne'd'aor lunhardenedgportions of the ammo" nium dichromate-albumin solution are thereupon washed off withzwater, whereupon, upon being .treated withan aqueous planographic etching or dampening solution, the platelisready for use.

While egg albumin is, in general, satisfactory for use in aqueous photo-sensitive lithographic printing solutions, it imparts to such solutions one objectionable characteristic, namely, a tendzencyito develop fungus mold rowth.

,I: have, found that blood albumin treated as [hereinafter described, may. advantageously be employed in photo-sensitive lithographic solutions in place'of egg albumin and-When so used .isfree from the-objectionable tendency ofegg albumin to promotefungus mold growth.

One' d fficulty, however, which I experienced and'had to overcome in connection with theuse of blood albumin in place of egg albumin in photosensitive lithographic solutions was the tendency of blood albumin to acquire an objectionable odor especially upon prolonged standing.

Another difiiculty which I encountered, and had to overcome, in the use of blood albumin in the resulting aqueous blood albumin solution is :rendered:permanently substantially odorless :iIaS well aasiclear *sandiifree from suspended colloidal matter and affords a highly satisfactoryzphotosensitive :lithographic solution. :which .has::.the advantage rover: egg: albumin solutions in that it is (substantially rfree ffrom :tendency toward fungus :mold growth.

Accordingly,.antobjectoof' theipresentinvention ilS' to'afforda bloodalbumin: photo-sensitive lithographic solution' which is substantially free from tendencytoward fungus :mold growth 'wliilejat :the same. time". being substantially permanently odorless. and clear :or .freev from colloidally suspended matter.

- Another object of the present invention is 1130 afford ai:novel,.rsimple and efficient-method of preparing thernew "photo-sensitive lithographic solution.

.sother. and further objects of the present invention willbe-apparent from the following description-and claims which, by way of illustration, illustrate ithe present invention and the I ;-principleszthereofcand what Inow consider. tobe photo-sensitive lithographic solutions was the l :the best mode in 'whiclr-I have 1c.0ntemplated1ap cplying .those ,principles. ithe invention embodying the same or equivalent Other'z embodiments :of

principles may be usedv and structural changes ..may.be made aszdesired-by those skilled in the .artwithoutdeparting from the present invention andthe purviewtof the appended claims.

.rA typical-process which may be followed ,in

,preparing thenew clarified and deodorized blood :albumin photo-sensitive lithographic solution is illustrated bythe following example:

"Example 71 grams of a good grade of powdered blood albumin (Armour) are dissolved in 1500 cc. of water and the resulting solution is then filtered to remove suspended colloidal matter. For this purpose ordinary chemical filter paper is un satisfactory in that such colloidal matter will pass directly through it. However, I have found that a filter aid composed essentially of a very finely divided diatomaceous earth, having a. particle size of such, for example, as the filter aid known commercially as J. M. Filtercel, affords a highly satisfactory filter in that it completely removes all suspended colloidal matter and affords a filtrate which is a clear aqueous blood albumin solution.

The thus filtered and clarified aqueous blood albumin solution is then deodorized by intimately mixing therein, with stirring, about 0.7 gram of finely divided activated charcoal, whereupon the mixture is agitated for approximately thirty minutes to afiord good contact of the finely divided activated charcoal particles with the aqueous blood albumin solution and resulting adsorption and removal of those substances in the solution which otherwise tend to impart an objectionable odor thereto.

The blood albumin-finely divided activated carbon mixture is then filtered again, by means of the finely divided diatomaceous earth filter aid referred to above, until the blackish cast imparted to the solution by the finely divided activated carbon is entirely removed and the solution is clear.

Approximately 19 grams of a finely divided watersoluble dichromate such, for example, as finely divided ammonium dichromate (NHi) 2C12O7, are then added to the solution, and stirred until dissolved therein, whereupon the hydrogen ion concentration or pH value of the resulting solution is adjusted by adding thereto a water solution of ammonia NH4OH until the pH of the solution is not substantially more nor substantially less than 9.1.

In place of the ammonium dichromate specified in the foregoing example equivalent quantities of sodium dichromate or potassium dichromate, or various mixtures of these three watersoluble dichromates, may be used.

The resulting solution is a clear, yellowish and odorless and otherwise highly satisfactory photosensitive ammonium dichromate-blood albumin lithographic solution which is permanently free from tendency toward fungus mold growth. The solution being more yellowish than red in color indicates the presence of chromate as well as dichromate ions in the solution possibly due to some chromate salt in the dichromate or to the decomposition of some of the dichromate althrough as to the exact cause of this I am not certain. In any event, however, the term dichromate as used herein and as used hereinafter in the claims is intended to and does include not only water-soluble dichromate salts but also any water-soluble chromate salt which may be added to or be present in the solution as an impurity or as a result of the decomposition of the dichromate, or otherwise.

It will thus be seen from the foregoing description that the present invention affords a new and improved photo-sensitive lithographic solution having the desirable advantages and characteristics hereinbefore set forth, and others which are inherent in the invention, and also affords a new, simple and efficient method of preparing said solution, and thus accomplishes its intended objects and has the desirable advantages and characteristics hereinbefore pointed out and others which are inherent in the invention.

I claim:

1. The method of preparing a clear, odorless and fungus mold resistant photo-sensitive lithographic solution which comprises dissolving powdered blood albumin in water, filtering the resulting aqueous blood albumin solution to remove suspended colloidal matter, deodorizing the thus filtered aqueous blood albumin solution by intimately stirring finely divided activated carbon therein, filtering the aqueous blood albuminfinely divided activated carbon mixture to remove the finely divided activated carbon therefrom, dissolving a water-soluble dichromate in the solution, and then adjusting the pH value of the resulting solution by adding an aqueous solution of ammonia thereto until the pH value of the solution is not substantially more nor substantially less than 9.1.

2. The method of preparing a clear, odorless, and fungus mold resistant photo-sensitive lithographic solution which comprises dissolving powdered blood albumin in water, filtering the resulting aqueous blood albumin solution to remove suspended colloidal matter therefrom, deodorizing the thus filtered aqueous blood albumin solution by intimately stirring finely divided activated carbon therein, filtering the aqueous blood albumin-finely divided activated carbon mixture to remove the finely divided activated carbon therefrom, then dissolving ammonium dichromate in the resulting solution, and then adjusting the pH value of the resulting solution by adding an aqueous solution of ammonia thereto until the pH value of the resulting solution is not, substantially more nor substantially less than 9.1.

CHARLES H. VAN DUSEN, J a.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 2,229,052 Dell Jan. 21, 1941 51,181 Hirsh Nov. 28, 1865 107,158 Bourgade Sept. 6, 1870 2,189,380 Littlefield Feb. 6, 1940 OTHER REFERENCES Eder, Ausfuhrliches Handbuch der Photographie Band. 4, 2 Tell (1926), entitled Das Pigemntverfahren, U. S. W., page 33. (Copy in Div. 7.) 

